Just had an email from Smithers asking how progress on my board was going,
from this thread,
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=39216
this is my reply.
Yep, finished it about 3 weeks ago. at least one design criteria is OK, I can grovel it in 12kt.
But so far I haven't quite managed to crack 33kts on it, possibly because I haven't achieved optimum set up yet.
There's quite a lot of initial drag, before the cutouts clear the water, feels like there's weed on the fin. half way round a gybe, feels like the brakes go on suddenly.
I think this is because the cutouts are acting like a curved surface, sucking the board down, not too sure, but in strong winds, (that it was designed for), this drag phase doesn't last very long, but the slow down in the gybes is annoying, means it won't be a good alpha board.
Spoke to our resident guru yesterday, Phil (Bugs) Smith, of Avalon Sail Co, (should have done that before I started the project). He says I shouldn't have made a smooth transition between the cutouts and the chamfer, it should be a sudden sharp step. (a bit forward of my bottom hand in the photo below)
Because the smooth transition will direct water into the cutouts, increasing drag.
I've also spoken to slowboat, he doesn't like the feet being so high off the water, as riders weight doesn't have the same stabilising control over the fin, and he could have a point here, the board feels very flighty.
I'll sail it a bit more, adjusting footstrap and mast track positions, seeing how good I can get it, then maybe I'll do some mods.
Here's it finished.
If ya feel game yet, I think would be good for a number of experienced as well as inexperienced sailors to have a try and get feedback from all.
From memory about 6kg before straps etc went on.
Woops got that wrong, just weighed it, and it's 6kg with pads and straps.
You've got 2 boards in 1, and if the extra hull creates too many hydrodynamic problems, the last thing you can try is to turn into one board which will resolve both issues boaught up by bugs and Slowie. Remove the step hull, you'll still have a board in the dimensions of a speed board, somewhere very close to the Missile 1, which was about 50cm wide.
Nice piece of work.
I would venture to guess that the sudden slowing down may be due to the curve of the step. When you slow down to a point where the planing surface cant support you and it sinks to the next level of support, the curved outline will be sucking water sideways.
That's my guess.
Thanks not wal, think you may have something there. If the rails were parallel, it probably wouldn't be as bad.
Great craftman ship mate. What Phil says about the cutouts sounds logical. Is there a reason why you made the back of the board so thick and hence the straps so high, were you after a lot of volume in the back for any reason